Vertical recirculating type vapor generator



Sept. 8, 1964 N. D. ROMANOS 3,147,743

VERTICAL RECIRCULATING TYPE VAPOR GENERATOR Filed May 8, 1962 v 2Sheets-Sheet 1 NICHOLAS D. ROMANOS 7 BY FIG.I Q63 ATTORNEY p 8, 1954 N.n. ROMANOS 3,147,743

VERTICAL RECIRCULATING TYPE VAPOR GENERATOR Filed May 8, 1962 2Sheets-Sheet 2 FIG.7

FIG. 6

INVENTOR: NICHOLAS D. ROMANOS ATTORNEY United States Patent poration ofDelaware Filed May 8, 1962, Ser. No. 193,206

6 Claims. (Cl. 122-32) The invention relates to a vapor generatorwherein a hot fluid is employed as a heating medium to generate vapor.More particularly, it relates to a shell and tube type vapor generatorwherein means are provided to establish continuous fluid circulationthrough the generator by defining distinct fluid paths therethrough.

These generator is arranged to occupy a minimum amount of space whiletransferring large quantities f heat. It comprises a vertically orientedbody defining a vapor generator chamber in which is located a tubebundle consisting of a plurality of heat exchanger tubes. Through thetubes is passed a heating medium comprising a hot liquid, such aspressurized water, liquid metal, petroleum or gas which gives up heat toa vaporizable liquid, such as water, whereby vapor is created. Thesocreated vapor leaves the unit through an outlet nozzle where it may bedirected to a vapor drum for further processing or to a prime moverwherein Work may be done.

With in the vapor generating chamber, baffle means are provided whichdefine downcomer and riser paths for the vaporizable liquid through theunit. The liquid which enters the generator is directed to the lowermostportion of the tube bundle by means of the downcomer paths and istransformed into vapor while flowing up the riser path around the hotliquid bearing heat exchanger tubes from which heat is extracted. Thechamber is divided into an evaporator zone and a superheater zone, thelimits of which are defined by the level of the liquid in the chamber.Additional baffle means are provided in the superheater zone to directthe vapor created in the evaporator zone across the heat exchanger tubesso as to impart a slight amount of superheat thereto thus superheatingthe vapor and eliminating any liquid that may be entrained in the vaporleaving the generator.

It is therefore a general object of the invention to provide a vaporgenerator characterized by compactness of form and efiiciency ofoperation.

A further object of the invention is to provide a vapor generatorwherein means are provided to accomplish vapor separation by means ofheat extraction from the heating liquid.

A still further object is to provide a natural circulation vaporgenerator of the recirculating type wherein vapor separation isaccomplished within the space occupied by the heat exchanger tubes.

Other objects and advantages will become apparent from the followingdescription when read in conjunction with the appended drawings wherein:

FIG. 1 is a vertical section of the novel vapor generator;

FIG. 2 is a section taken along line 22 of FIG. 1;

FIG. 3 is a section taken along line 33 of FIG. 1;

FIG. 4 is a section taken along line 44 of FIG. 1; and

FIGS. 57 are modified forms of vapor generators employing the instantinvention.

Referring now to FIG. 1, there is shown a vapor generator 19 comprisinga vertically elongated, cylindrical body 11 having both of its endsclosed by means of substantially hemispherically shaped heads 12 and 13thereby defining a closed pressure vessel 14. Adjacent the upper end ofthe vessel 14 a tube sheet 15 is weldedly united to the wall thereofthus dividing the vesse1 14 into two fluidly apertures 42 to receive andalign the tubes 21. Smaller.

distinct portions, the upper portion being designated the hot fluidchamber 16 and the lower portion, the vapor generating chamber 17. Thetube sheet 15 has disposed therein an enlarged, centrally locatedaperture 18. Superposed upon the tube sheet 15, in axial alignment withthe aperture 18, is a vapor outlet nozzle 19, the upper end of whichextends through the upper head 12. The nozzle 19 comprises a cylindricalmember which is weldedly attached to both the tube sheet 15 and theupper head 12 and permits withdrawal of the vapor created in the vaporgenerating chamber,

Tube seats 20 are formed in the tube sheet 15 and receive the ends of aplurality of heat exchanger tubes 21. These tubes are U-shaped andcomprise a tube bundle 22 which extends into the vapor generatingchamber 17 substantially filling the same. Partitions in the form of apair of plates 23 which conform to the walls of the hot fluid chamber 16are attached to the tube sheet 15, head 12 and nozzle 19 in a fluidimpervious manner so as to divide the hot fluid chamber 16 into inletand outlet portions 24 and 25. Inlet and outlet nozzles 26 and 27communicate with the respective portions and permit continuous flow of aheating medium to the generator 10 from a source (not shown).

The arrangement of the tubes 21 forming the tube bundle 22 is such thatan axially disposed void extends throughout the length of the bundle.Within this void is located an annular baffle plate in the form of anenlarged conduit 28 which is mounted in concentric relation with thetube bundle along the longitudinal axis of the vessel 14. The conduit 28is open at both its upper and lower ends and extends from a pointremoved from the upper end of the vapor generating chamber 17 to a pointspaced from the lower end of the vessel 14 so as to establish adowncomer path 29 to the lower end of the vessel. A second annularbafile plate 30, which is substantially coextensive with the first, ismounted in concentric relation therewith. It surrounds the tube bundle22 and is spaced from the inner wall of the vessel 14 so as to establisha second, outer downcomer path 31. Be tween the two baflies there isthus formed a riser path 32 through which the tubes 21 of the tubebundle 22 extend.

Annular support plates 41 are attached to the battles 28 and 30 atspaced points therealong. These plates extend between the baflles andare provided with a plurality of apertures 43 are provided in the platesto permit the passage of fluid therethrough.

Feedwater is admitted to the generator by means of a feedwater inletnozzle 33 which communicates with the central downcomer path by means ofa feedwater duct 34. During normal operation of the generator, a body ofliquid occupies the lower portion of the vapor generatlng chamber 17 andhas a level 35 spaced a considerable distance from the tube sheet 15thereby dividing the chamber 17 into an evaporator zone and a superheatzone. A hollow partition 48 extends the length of chamber 17 and fillsan empty portion of the tube bundle to compel the flow of fluid acrossthe tubes 21. Within the superheat zone a plurality of bafile plates areprovided which define a path over which the vapor flows across the heatexchanger tubes. Some of these plates, such as those designated as 36,are attached to the tube bundle Patented Sept. 8, 1964v to the Vapor.Bafiie plates 36 may be provided with central openings 39 which areclosed during operation of. the generator by means of cover plates 40.Removal of the cover plates 40 establishes a convenient means forobtaining access to the lower portion of the vapor generating chamber 17in order to inspect or service the generator internals.

The operation of the herein disclosed vapor generator is as follows. Ahot fluid, such as pressurized water, liquid metal, petroleum or gas isadmitted to the inlet portion 24 of the hot fluid chamber 16 by means ofthe nozzle 26. It flows through the tubes 21 of the tube bundle 22 whereit gives up heat before leaving the generator through the outlet nozzle27. A vaporizable liquid, such as water, is admitted to the vaporgenerating portion 17 of the generator through the feedwater inletnozzle 33 from whence it flows through the feedwater duct 34 into thecentral downcomer conduit 28 and thence to the lower portion of thevapor generating chamber 17. As shown in FIG. 1, the liquid level 35 inthe vapor generating chamber 17 is normally above the upper ends of theannular baffle plates 28 and 30 therefore a portion of the liquid iscaused to flow to the bottom of the generator 10 through the outerdowncomer path 31 thereby creating recirculation of the fluid.

Due to the thermal siphonic effect of the heat given off by the hotfluid flowing through the heat exchanger tubes 21, the vaporizableliquid is caused to flow upwardly around the tubes through the riserpath 32 whereby some of the fluid is transformed into vapor. Uponreaching the superheater zone of the chamber 17 the vapor is caused toflow along the tortuous path formed by the baflie plates 36 and 37around the exposed surfaces of heat exchanger tubes 21 which thus impartan amount of superheat to the vapor thereby removing any water which maybe entrained in the vapor before it leaves the generator 10 through theoutlet nozzle 19.

In FIGS. 5, 6 and 7 there are shown various modified arrangements of thepresent invention. In FIG. there is shown a vapor generator arrangementwherein the generator 10' is inverted from the arrangement shown inFIG. 1. In this arrangement the nozzle 44 permits withdrawal of thevapor from the upper end of the generator while the cylinder 19' whichextends between the tube sheet and the head 12 is capped by means of acover plate 45, the latter serving as a drain or as a means of obtainingaccess into the generating portion of the vessel in order to inspect orservice the interior thereof. In the FIG. 6 arrangement the vessel 14 isprovided with a pair of tube sheets 15 and 15", each being positioned ateither end of the vessel, thereby providing hot fluid chambers at eachend thereof with the vapor generating chamber 17 being positionedtherebetween. Tube sheet 15" is similar to the tube sheet 15 of FIG. 1but the aperture 18 is omitted from tube sheet 15" so as to close thebottom of the vapor generating chamber. In this arrangement the tubebundle 22" consists of a plurality of straight tubes 46 which extendthrough the vapor generating chamber 17 The upper hot fluid chamber 24"receives fluid from a source, not shown, by means of the inlet nozzle26. This fluid flows through the tube bundle 22" to the lower chamber25" from whence it passes through the central outlet nozzle 27" by meansof apertures 43 formed therein. A vapor outlet means is provided in theupper portion of the generator by means of the cylindrical nozzle 19which extends from the tube sheet through the upper head 12". The FIG. 7arrangement is substantially the same as that shown in FIG. 5 with theexception that a portion 50 of the tube bundle 22 is formed so as to bemaintained below the liquid level 35 in the vapor generating chamber.This expedient provides a means of controlling the amount of superheatimparted to the vapor by limiting the amount of heating surface to whichthe vapor is exposed. It also permits the use of a lower grade materialin forming the tubes which are maintained below the liquid level sincethese tubes are continuously submerged in water and thus not exposed tothe danger of sealing as are the tubes which extend above the waterlevel.

By means of the present invention there is provided a vapor generatingunit which is characterized by compactness of form and efliciency ofoperation. The unit is disposed in a vertical attitude thereby reducingthe amount of floor space occupied thereby while the shell and tubearrangement permits the exposure of a large amount of heating surfacefor the transforming of liquid into vapor. The efiiciency of the unit isenhanced by the provision of a downcomer means which permits therecirculation of liquid within the vapor generating chamber.

While there has been disclosed several particular embodiments of theinvention, this disclosure is intended to merely illustrate and not tolimit the inventive concept. It is understood that changes may be madein the form of the apparatus disclosed without departing from the spiritof the appended claims.

What is claimed is:

l. A vapor generator comprising a vertically elongated body forming asubstantially closed vapor generating chamber; a plurality of fluidconducting tubes extending into said chamber; means for effecting a flowof heating fluid through said tubes; conduit means open at both endsextending longitudinally of said chamber and terminating short of theends thereof for conducting vaporizable liquid to the bottom of saidchamber, said conduit means being spaced from the wall of said chamberto form downcomer and riser passages therein; means communicating withsaid downcomer passage for admitting vaporizable liquid thereto, saidvaporizable liquid filling said chamber to a level above the top of saidconduit means but spaced from the top of said chamber to divide saidchamber into an evaporating space and a superheating space immediatelythereabove; all of said tubes being immersed at least to a substantialdegree in said vaporizable liquid to provide heating surface for saidevaporating space; at least some of said tubes extending above the levelof said vaporizable liquid to provide heating surface for saidsuperheating space; vapor outlet means communicating with saidsuperheating space; and bafile means positioned in said superheatingspace between said liquid level and said vapor outlet means fordirecting vapor generated in said evaporating space cross the tubesurface located in said superheating space prior to its passing throughsaid vapor outlet means. 7

2. A vapor generator comprising a vertically elongated body forming asubstantially closed vapor generating chamber; a plurality of fluidconducting tubes forming a tube bundle extending into said chamber, saidtube bundle having a length and width to be substantially co-extensivewith said chamber; means for effecting a flow of heating fluid throughsaid tubes; conduit means open at both ends extending longitudinally ofsaid chamber and terminating short of the ends thereof for conductingvaporizable liquid to the bottom of said chamber, said conduit meansbeing spaced from the wall of said chamber to form downcomer and riserpassages therein; means communicating with said downcomer passage foradmitting vaporizable liquid thereto, said vaporizable liquid fillingsaid chamber to a level above the top of said conduit means but spacedfrom the-top of said chamber to divide said chamber into an evaporatingspace and a superheating space immediately thereabove; all of said tubesbeing immersed at least to a substantial degree in said vaporizableliquid defining said evaporating space to provide heating surfacetherefor; at least some of the tubes of said tube bundle extending abovethe level of said vaporizable liquid into said superheating space toprovide heating surface therefor; vapor outlet means communicating withsaid superheating space; and bafi'le means positioned in saidsuperheating space between said liquid level and said vapor outlet meansfor directing vapor generated in said evaporating space across the tubesurface located in said superheating space prior to its passing throughsaid vapor outlet means.

3. A vapor generator comprising a vertically elongated cylindrical body;arcuate heads attached to the ends of said body to form a substantiallyclosed vessel; tube sheet means within said vessel dividing the sameinto a hot fluid section and a vapor generating chamber; a plurality offluid conducting tubes attached to said tube sheet means in fluidcommunication with said hot fluid section forming a tube bundle, saidtube bundle extending into said chamber and having a length and Width tobe substantially coextensive therewith; means communicating with saidhot fluid section for effecting the flow of hot fluid through saidtubes; elongated conduit means positioned within said vapor generatingchamber and terminating short of the ends thereof for conductingvaporizable liquid to the bottom of said chamber, said conduit meansbeing concentrically related to the Wall of said chamber and spacedtherefrom to form downcomer and riser passages within said chamber;means communicating with said downcomer passage for admittingvaporizable liquid thereto, said vaporizable liquid filling said chamberto a level above the top of said conduit means but spaced from the topof said chamber to form an evaporating space and a superheating spaceimmediately thereabove; all of the tubes of said tube bundle beingimmersed at least to a substantial degree in the vaporizable liquiddefining said evaporating space to provide heating surface therefor; atleast some of said tubes extending above said level of vaporizableliquid into said superheating space to provide heating surface therefor;vapor outlet means communicating with said superheating space; andbaflle means including a plurality of axially spaced plates extendinglaterally of said tube bundle defining radially spaced openings fordirecting the vapor generated in said evaporating space along a tortuouspath across the tube surface located in said superheating space prior toits passing through said vapor outlet means.

4. A vapor generator organization as recited in claim 3 wherein saidtube sheet means comprises a single tube sheet located in the upperportion of said vessel dividing the same into an upper hot fluid sectionand a lower vapor generating chamber and said tube bundle comprises aplurality of U-shaped tubes attached to said tube sheet and dependingtherefrom.

5. A vapor generator organization as recited in claim 3 wherein saidtube sheet means comprises a single tube sheet located in the lowerportion of said vessel dividing the same into a lower hot fluid sectionand an upper vapor generating chamber and said tube bundle comprise aplurality of U-shaped tubes attached to said tube sheet and verticallyextending therefrom.

6. A vapor generator organization as recited in claim 3 wherein saidtube sheet means comprises a first tube sheet located in the upperportion of said vessel and a second tube sheet located in the lowerportion of said vessel spaced from said first tube sheet therebydefining an upper hot fluid inlet section, a lower hot fluid outletsection and a vapor generating chamber therebetween and said tube bundlecomprises a plurality of straight tubes extending between said tubesheets and having their ends attached to said tube sheets.

References Cited in the file of this patent UNITED STATES PATENTS2,922,404 Kopp et a1. Jan. 26, 1960 FOREIGN PATENTS 745,563 Germany Aug.12, 1944 841,656 Great Britain July 20, 1960

1. A VAPOR GENERATOR COMPRISING A VERTICALLY ELONGATED BODY FORMING ASUBSTANTIALLY CLOSED VAPOR GENERATING CHAMBER; A PLURALITY OF FLUIDCONDUCTING TUBES EXTENDING INTO SAID CHAMBER; MEANS FOR EFFECTING A FLOWOF HEATING FLUID THROUGH SAID TUBES; CONDUIT MEANS OPEN AT BOTH ENDSEXTENDING LONGITUDINALLY OF SAID CHAMBER AND TERMINATING SHORT OF THEENDS THEREOF FOR CONDUCTING VAPORIZABLE LIQUID TO THE BOTTOM OF SAIDCHAMBER, SAID CONDUIT MEANS BEING SPACED FROM THE WALL OF SAID CHAMBERTO FORM DOWNCOMER AND RISER PASSAGES THEREIN; MEANS COMMUNICATING WITHSAID DOWNCOMER PASSAGE FOR ADMITTING VAPORIZABLE LIQUID THERETO, SAIDVAPORIZABLE LIQUID FILLING SAID CHAMBER TO A LEVEL ABOVE THE TOP OF SAIDCONDUIT MEANS BUT SPACED FROM THE TOP OF SAID CHAMBER TO DIVIDE SAIDCHAMBER INTO AN EVAPORATING SPACE AND A SUPERHEATING SPACE IMMEDIATELYTHEREABOVE; ALL OF SAID TUBES BEING IMMERSED AT LEAST TO A SUBSTANTIALDEGREE IN SAID VAPORIZABLE LIQUID TO PROVIDE HEATING SURFACE FOR SAIDEVAPORATING SPACE; AT LEAST TO OF SAID TUBES EXTENDING ABOVE THE LEVELOF SAID VAPORIZABLE LIQUID TO PROVIDE HEATING SURFACE FOR SAIDSUPERHEATING SPACE; VAPOR OUTLET MEANS COMMUNICATING WITH SAIDSUPERHEATING SPACE; AND BAFFLE MEANS POSITIONED IN SAID SUPERHEATINGSPACE BETWEEN SAID LIQUID LEVEL AND SAID VAPOR OUTLET MEANS FORDIRECTING VAPOR GENERATED IN SAID EVAPORATING SPACE CROSS THE TUBESURFACE LOCATED IN SAID SUPERHEATING SPACE PRIOR TO ITS PASSING THROUGHSAID VAPOR OUTLET MEANS.